Hearing aid technology continuously strives toward developing smaller hearing aids or hearing instruments. This development is helped by a continuous reduction in size for all components commonly utilised in hearing aids.
The advent of in-the-canal (ITC) type of hearing aids and completely-in-the-canal (CIC) type of hearing aids has brought several benefits to hearing aid users. Many users or potential users find it cosmetically attractive to wear an aid that may be completely contained within the ear canal, since this renders the aid invisible, at least in a majority of everyday situations.
Further, hearing aids of the ITC and CIC types provide acoustical benefits compared to a behind-the-ear (BTE) type of instrument. One benefit is improved directional hearing due to a major part of the outer ear being left unblocked by the ITC and CIC hearing aids, thereby preserving the natural directional properties of the outer ear.
While the cosmetic and acoustic improvements related to the use of ITC and CIC hearing aids are well recognised, there remain a number of practical problems related to the daily use and operation of these types of aids.
A hearing aid is usually provided with one or several control means, such as push buttons, switches, etc., which may be located on a face part of the hearing aid housing.
The control means may be adapted to provide a number of functions, such as turning the aid on/off, controlling a gain, changing between a number of predetermined listening programs, changing between a microphone signal and a telecoil signal, etc.
A first practical problem is the difficult operation of controlling means mounted on the face of the housing of the hearing aid. This problem originates from e.g. the inaccessible position of the hearing aid deep inside the ear canal, which normally makes it difficult for a user to find and properly operate the controlling means. The very limited available area of the face part of the aid further adds to this problem, since any controlling means must have very small physical dimensions to fit on the face of the housing. This problem is pronounced for elderly people, which constitute the majority of hearing aid users, since they often have reduced capability to perform the necessary tiny movements of the controlling means with their fingertips.
A second problem is that it may be very difficult for the user to remove an ITC and especially a CIC type aid from its clamped-in position in the ear canal.
A solution to the problem of removing the aid is disclosed in U.S. Pat. No. 5,381,484 wherein a pull-out string with beads is attached to a face part of a housing of a CIC aid. The beads provided on the string enables the user to get a firm grip on the string and apply the force necessary to release the aid.
This solution, however, creates a derived third problem, since, during the release process, an acoustic leakage path is inevitably created in the ear canal between the microphone mounted on the face part and a sound emitting transducer (receiver) of the hearing aid. This leakage path will usually make the hearing aid oscillate at a high frequency and at full output power, producing a sustained and highly irritating noise into the ear of the user until the battery supply is turned off, or the gain is turned down. Also, a string pointing out of the ear is not desirable for cosmetic reasons.